Abstract
We present an analysis of the photometric variability of M dwarfs in the Wide Field Camera (WFCAM) Transit Survey. Although periodic light-curve variability in low mass stars is generally dominated by photospheric star spot activity, M dwarf variability in the J band has not been as thoroughly investigated as at visible wavelengths. Spectral type estimates for a sample of over 200 000 objects are made using spectral type-colour relations, and over 9600 dwarfs (J <17) with spectral types later than K7 were found. The light curves of the late-type sample are searched for periodicity using a Lomb-Scargle periodogram analysis. A total of 68 periodic variable M dwarfs are found in the sample with periods ranging from 0.16 to 90.33 d, with amplitudes in the range of similar to 0.009 to similar to 0.115 in the J band. We simulate active M dwarfs with a range of latitude-independent spot coverages and estimate a periodically variable fraction of 1-3 per cent for stars where spots cover more than 10 per cent of the star's surface. Our simulated spot distributions indicate that operating in the J band, where spot contrast ratios are minimized, enables variability in only the most active of stars to be detected. These findings affirm the benefits of using the J band for planetary transit searches compared to visible bands. We also serendipitously find a Delta J > 0.2 mag flaring event from an M4V star in our sample.
Original language | English |
---|---|
Pages (from-to) | 3358-3373 |
Number of pages | 16 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 427 |
Issue number | 4 |
DOIs | |
Publication status | Published - Dec 2012 |
Keywords
- stars: activity
- stars: late type
- stars: starspots
- stars: variables: general
- SKY SURVEY DATA
- LOW-MASS STARS
- SCALE MAGNETIC TOPOLOGIES
- FIELD M-DWARFS
- MONITOR PROJECT
- MAIN-SEQUENCE
- TIME-SERIES
- SPACED DATA
- COOL STARS
- MID-M